Power failure protective system



July 28, 1942. c. H. DICKE POWER FAILURE PROTECTIVE SYSTEM Filed May 25,1940 Wa w l A a Y [B Patented July 28, 1942 POWER FAILURE PROTECTIVESYSTEM Carl H. Dicke, Dayton, Ohio, assignor to The Master ElectricCompany, a corporation of Ohio Application May 25, 1940, Serial No.337,131

Claims.

This invention relates to a power failure protective system, and moreparticularly to one for use in connection with damper controllingapparatus for a furnace.

An object of this invention is to provide a simple and sure arrangementfor protecting electrically controlled apparatus upon the occurrence ofa power failure.

Another object of this invention is to prevent the overheating of anelectrically controlled heating system upon the occurrence of a powerfailure.

Still another object of this invention is to provide an arrangement formoving the dampers of a furnace to the combustion-retarding positionupon failure of the power source and de-energization of the electricaldamper controlling apparatus.

Further objects and advantages of this invention will be apparent fromconsideration of the specification as illustrated by the accompanyingdrawing of a possible embodiment of the invention, in which drawing thesingle figure illustrates partially schematically and partiallydiagrammatically the novel apparatus and circuit connections thereof,forming a preferred embodiment 'of the present invention as applied tothe control of a furnace damper.

As seen in the single figure of the accompanying drawing, the inventionis applied to a furnace, generally indicated at It! controlled by adamper motor generall indicated at [2. The damper motor I2 is ofgenerally familiar structure in which the motor proper first drives apinion l4 and, through a series of reduction gears l6 drives a finalwheel l8 with which there is rotatably connected as by a common shaft aslotted control arm 29. Through any suitable arrangement known in theart per se, such as a wire or chain 22 guided by pulley 24, rotation ofthe arm 29 in the direction of the arrow upon energization of the dampermotor 12 is adapted to raise a draft damper 28 of the furnace ill. Atthe same time, and as is also well known to the art, opening of thedraft damper 26 may take place simultaneously with the closing of asuitable check damper (not shown). Closure of the draft damper 26(and/or opening of the check damper) is effective by suitable means suchas a spring 2! which is stretched upon movement of the arm 20 to theposition corresponding to the open position of the draft damper (asindicated in dotted lines). The closure operation effected by the spring2| will be explained in more detail hereinafter.

The control of the furnace dampers is adapted to be initiated by asuitable thermo-responsive switch, generally but not necessarily a roomthermostat indicated at 28. Closure of the thermoresponsive switch 28completes an energizing circuit for the damper motor [2 through a secondswitch 30, whose function will also be later described, This energizingcircuit for the damper motor l2 arises from a source of power indicatedat 32 and may be traced from one side of the secondary winding of atransformer 34, connected to the source of power, conductors 35 and 38,the damper motor I 2, conductor 40, normally closed contacts 42 and 44and the switch arm 46 of the switch 30, conductors 48 and 5B, bimetallicarm 52 and contacts 54 and 56 of the thermo-responsive device 28, andconductor 58 to the other side of the secondary winding of thetransformer 34. The motor will now rotate in such a direction as to movethe arm 28 in the counter-clockwise direction until the damper 26 hasbeen raised, which corresponds to the dotted position of the arm 20 asshown in the drawing. At the same time, the wheel It will have rotatedto such an extent that means such as a pin 69 mounted thereon willcontact the arm 62 of the switch 30. The switch 30 is preferably of anywell-known snap action type, diagrammatically illustrated here as atoggle switch, so that movement of the arm 62 by the pin 66 will movethe contact arm 46 and its contact 44 from the stationary contact 42 tothe stationary contact M. This switch movement breaks the circuit to thedamper motor l2, but substantially simultaneously establishes a circuitfor the solenoid $6. This circuit may be traced from one end of thesecondary winding of transformer 34 to conductor 68, solenoid winding66, conductor 10, contacts 64 and 44 and arm 46 of the switch 36,conductors 48 and 50, switch arm 52 and still closed contacts 54 and 55of the thermo-responsive element 28, and conductor 58 to the other sideof the secondary winding. Energization of the solenoid 66 effectsmovement of a double-arm lever 12, one end of which is provided withmeans such as the teeth 14 for en gaging and locking the pinion M of thegear train connected to the wheel it. Thus, despite the fact that thedamper motor is now de-energized, the arm 20 and the damper 26 will notreturn to their original (closed) position under the action of thespring 2 l, but will be locked in the open position. The furnace damper26 will accordingly will be held open until either one of two conditionsoccurs. If the condition within the space to be heated is such that thethermostat 28 becomes satisfied, the contact arm 52 thereof will move tothe off position thus breaking the circuit to the solenoid E6. The lever12 will then act under the force of suitable return means such as thespring 16 to release the pinion l4 and the arm 2t will then, under thereturn action of the tensioned spring 2| move to its original positionto close the damper 26. Simultaneously, the switch 39 which is normallybiased by any suitable means to maintain the circuit to the damper motorwill return to its original position, so that the system as a whole isnow prepared to again raise the damper due to a call of the thermostat28, Similarly, the furnace damper 26 will be closed upon the occurrenceof any power failure, since, the solenoid 66 is connected across thesecondary winding of the transformer 34, as was previously traced. Thisfeature of the system is extremely important to prevent overheating ofthe furnace in case of a power failure, with the consequent waste offuel and actual danger of conflagration. Upon the return of power, thesystem is prepared to again open the furnace damper if the thermostat 28so specifies.

The system above described may be used in connection with a signal andpre-heating lamp T8 for the thermo-responsive element 28, which willonly be lighted when the thermostat calls for heat. The circuit for thelamp 23 may be traced from one side of the secondary winding of thetransformer 34, conductors 36 and 80, the lamp [8, conductors 82 andswitch arm 52 and contacts 54 and 55 of th thermo-responsive element 28,and conductor 58 to the other side of the secondary winding.

It will be at once obvious to those skilled in this art, that manymodifications and different applications of the above described systemare possible. In the first place, the system can be used to control afurnace other than by control of the damper. Also, the system isapplicable to the control of other devices than a furnace, which mayproduce a variablebut controllable condition. Additionally, I do notintend that the invention be limited to include the precise structuralelements shown and described. For example, the snap switch, illustratedas a toggle switch, can be of any standard construction and be actuatedby the damper motor in any on of several wel1 known and obvious ways.The thermo-responsive switch may also be of any standard constructionand, moreover, if the condition to be controlled is not heat-responsive,the switch could be responsiv to any controllable condition as, forexample, pressure. While a motor has been illustrated as supplying thepower for raising the furnace damper, it is also to be understood thatother electromotive devices might be substituted therefor. The type ofreturn spring and its particular interconnection with the controlmechanism is of no importance. While the type illustrated is to bepreferred, other types of springs, as for example, a spiral spring couldalso be used, or a spring Of the character illustrated could beconnected to the damper itself or in any other manner to return thesystem to its original position upon power failure or the opening of thecontrol switch 28. The illustration of the electro magnetic brake ismerely diagrammatic, and this, too, could be formed in any manner solong as it performs its locking function upon disconnection of thedamper motor.

Accordingly while the form of mechanism here shown and described isadmirably adapted to fulfill the object primarily stated, it is to beunderstood that it is not intended to confine the invention to the oneform of embodiment herein disclosed, for it is susceptible of embodimentin various forms all coming within the scope of the claims which follow.

I claim:

1. In a damper controlling system, in combination, a furnace dampermovable between first and second control positions, a damper motorincluding a gear train driven by said motor and a rotatable arm drivenby said gear train, means interconnecting said arm with said damper formovement of the latter by the former, a source of power, athermo-responsive switch, a singlepole, double-throw snapaction switchnormally biased to one closed position, conductors connecting said motorto said source of power through the normally closed contacts of saidsingle-pole, double-throw switch and said thermoresponsive switch insuch a manner as to energize said motor to drive said gear train in adirection to move said damper from its first to its second position, anelectro-magnet, means operated upon energization of said electro-magnetfor locking said gear train conductors serially connecting saidelectro-magnet to said source of power through the normally opencontacts of said single-pole, double-throw switch and through saidthermo-responsive switch, means carried by said gear train for actuatingsaid single-pole, double-throw switch to close its normally opencontacts and open its normally closed contacts, when said gear train hasbeen moved to a position corresponding to the second position of saiddamper, whereby said braking means will hold the gear train and damperin this position during closure of said thermo-responsive switch andmaintenance of said power source, and mechanical means continuallyurging return of said gear train and damper to the first position,whereby upon opening of said thermo-responsive switch or failure of saidpower source, said damper will be returned to its first position.

2. The combination according to claim 1, in which said mechanical meanscomprises a spring.

3. The combination according to claim 1, in which said mechanical meanscomprises a spring connected to and tensioned by movement of said armcorresponding to movement of said damper from the first to the secondcontrolling position.

4. The combination according to claim 1, in combination with a signallight mounted in juxtaposition to said thermo-responsive switch andconnected in parallel to th serially connected motor and normally closedsingle-pole, doublethrow switch contacts.

5. The combination according to claim 1, in which said single-pole,double-throw switch is mounted in juxtaposition to said damper motor,and the means carried by said gear train comprises a pin projecting fromone of the gears and movable into engagement with said switch.

CARL H. DICKE.

